FinFET Body Contact and Method of Making Same

ABSTRACT

A semiconductor device may include body contacts on a finFET device for ESD protection. The semiconductor device comprises a semiconductor fin, a source/drain region and a body contact. The source/drain region and the body contact are in the semiconductor fin. A portion of the fin is laterally between the source/drain region and the body contact. The semiconductor fin is on a substrate.

This application is a divisional of U.S. application Ser. No.13/363,026, entitled “FinFET Body Contact and Method of Making Same,”filed on Jan. 31, 2012, which application is incorporated herein byreference.

BACKGROUND

Transistors are key components of modern integrated circuits. To satisfythe requirements of increasingly faster speed, the drive currents oftransistors need to be increasingly greater. Since the drive currents oftransistors are proportional to gate widths of the transistors,transistors with greater widths are preferred.

The increase in gate widths, however, conflicts with the requirements ofreducing the sizes of semiconductor devices. Fin field-effecttransistors (finFET) were thus developed.

The introduction of finFETs has the advantageous feature of increasingdrive current without the cost of occupying more chip area. However,finFET transistors raise numerous issues relating to electrostaticdischarge (ESD) performance.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present embodiments, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIGS. 1A and 1B illustrate in perspective view and cross-sectional view,respectively, a finFET in accordance with an embodiment;

FIGS. 2A through 8 illustrate steps in the manufacture of the structureillustrated in FIGS. 1A and 1B;

FIG. 9 illustrates in cross-sectional view, a second illustrativeembodiment of a finFET device structure; and

FIGS. 10A and 10B illustrate in top-down view and cross-sectional view,respectively, a second illustrative embodiment of a finFET devicestructure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Various steps in the formation of a fin device will be described withreference to FIGS. 2A through 8. Reference will now be made in detail toembodiments illustrated in the accompanying drawings. Wherever possible,the same reference numbers are used in the drawings and the descriptionto refer to the same or like parts. In the drawings, the shape andthickness may be exaggerated for clarity and convenience. Thisdescription will be directed in particular to elements forming part of,or cooperating more directly with, methods and apparatus in accordancewith the present disclosure. It is to be understood that elements notspecifically shown or described may take various forms well known tothose skilled in the art. Many alternatives and modifications will beapparent to those skilled in the art, once informed by the presentdisclosure.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrases “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.Furthermore, the particular features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments. It shouldbe appreciated that the following figures are not drawn to scale;rather, these figures are merely intended for illustration.

FIG. 1A illustrates a perspective view of a finFET device 50, whichincludes a substrate 110, a fin 120 above the substrate 110, anisolation region 130 surrounding the fin 120, a gate 180 over the fin120, source/drain regions 140, and body contacts 150. In an embodiment,substrate 110 may be bulk substrate, such as a bulk silicon wafercommonly employed in CMOS manufacturing processes. Alternatively,substrate 110 may be a compound substrate, such as asilicon-on-insulator (SOI) substrate, or another bulk or compoundsemiconductor substrate formed of other materials such as germanium,gallium-arsenide, III-V materials, and the like. Only a portion ofsubstrate 110 is illustrated in the figures, as this is sufficient tofully describe the illustrative embodiments.

The fin 120 is formed as a vertical silicon fin extending above thesubstrate 110, and is used to form the source/drain regions 140, achannel region (not shown) between the source and drain regions, and thebody contacts 150. A gate dielectric layer (not shown) may be formed inthe channel region. The gate 180 is then formed around the fin 120 andwraps the fin 120 in the channel region. FinFET device 50 may alsoinclude four dummy gates 182 (not shown in FIG. 1A for clarity) over thefin 120 with two dummy gates 182 on each side of the gate 180.

The isolation region 130 may be shallow trench isolation (STI) regions,and may be formed by etching the substrate 110 to form a trench andfilling the trench with a dielectric material. In accordance with anembodiment, the isolation regions may be filled with a dielectricmaterial such as an oxide material, a high-density plasma (HDP) oxide orthe like.

FIG. 1B is a cross-sectional view of an embodiment of the finFET device50 from the Z plane along the X-X line of FIG. 1. FIG. 1B illustrates anembodiment of the finFET device 50 that includes a gate 180 and fourdummy gates 182 over the fin 120 with each gate including a dielectriclayer 170 between the gate and the fin 120 and gate spacers 190 on thesides of the gate. In an illustrative embodiment, the fin material issilicon doped with appropriate dopant impurities. There are two dummygates 182 on each side of the gate 180. The two dummy gates 182 closestto the gate 180 may be used for self-aligned dopant implantation of thesource/drain regions 140 and the body contacts 150. The source/drainregions 140 are doped to make these portions of fin 120 conductive. Thebody contacts 150 are also doped to make these portions of the fin 120conductive, but they may be doped with a conductivity type opposite ofsource/drain regions 140. For example, if the source/drain regions 140are doped with an n-type dopant, the body contacts 150 may be doped witha p-type dopant. In another embodiment, the source/drain regions 140 andthe body contact 150 could be formed by first forming recesses and thenepitaxially growing the source/drain regions 140 and body contacts 150by selective epitaxial growth (SEG). In an embodiment, non-selectiveepitaxial growth could be employed. The source/drain regions 140 andbody contacts 150 may be doped either through an implantation method asdiscussed below, or else by in-situ doping as the material is grown. Thesource/drain regions 140 and the body contacts 150 may include anelectrode layer 160. The electrode layer 160 may comprise a conductivematerial and may be selected from a group comprising ofpolycrystalline-silicon (poly-Si), poly-crystalline silicon-germanium(poly-SiGe), metallic nitrides, metallic silicides, metallic oxides, andmetals.

The outer dummy gates 182 may be located partially on the isolationregion 130 and partially on the body contacts 150. In anotherembodiment, the outer dummy gates 182 may be located entirely on theisolation region 130. In yet another embodiment, the outer dummy gates182 may be located entirely on the body contacts 150. The four dummygates 182 may be used to provide a more even density for a planarizingprocess of the gates, such as chemical mechanical polishing (CMP).

FIGS. 2A through 8 illustrate a process to form a finFET deviceaccording to an embodiment. The figures are cross-sectional views fromthe Z plane along either the Y-Y line or the X-X line of FIG. 1. Eachfigure displays the axis that the cross-sectional view is from. Althoughthis embodiment is discussed with steps performed in a particular order,steps may be performed in any logical order.

FIGS. 2A and 2B illustrate the finFET device at some point duringprocessing. The device includes a semiconductor layer 210 on a substrate110. As discussed above, semiconductor layer 210 may comprise bulksilicon or an active layer of a silicon-on-insulator (SOI) substrate.The semiconductor layer 210 may be doped through an implantation process220 to introduce p-type or n-type impurities into the semiconductorlayer 210.

In FIGS. 3A and 3B, the fin 120 is formed by patterning thesemiconductor layer 210. The fin patterning process may be accomplishedby depositing a commonly used mask material (not shown) such asphotoresist or silicon oxide over the semiconductor layer 210. The maskmaterial is then patterned and the semiconductor layer 210 is etched inaccordance with the pattern. In this manner, a semiconductor structureof a semiconductor fin overlying a substrate may be formed. Asillustrated in FIGS. 3B, the fin 120 extends along the line X-X ofFIG. 1. In an alternative embodiment, fin 120 may be epitaxially grownfrom a top surface of substrate 110 within trenches or openings formedin a patterned layer atop substrate 110. Because the process is known inthe art, the details are not repeated herein. In an embodiment, as shownin FIGS. 3A and 3B, the fin 120 may have a width 320 of betweenapproximately 2 nm and 20 nm and a height 310 of between 7 nm and 50 nm.

FIGS. 4A and 4B illustrate the formation of the gate dielectric layer170. The gate dielectric layer 170 may be formed by thermal oxidation,CVD, sputtering, or any other methods known and used in the art forforming a gate dielectric. In other embodiments, the gate dielectriclayer 170 includes dielectric materials having a high dielectricconstant (k value), for example, greater than 3.9. The materials mayinclude silicon nitrides, oxynitrides, metal oxides such as HfO₂,HfZrO_(x), HfSiO_(x), HfTiO_(x), HfAlO_(x), and the like, andcombinations and multi-layers thereof. In another embodiment, the gatedielectric layer 170 may have a capping layer selected from metalnitride materials such as titanium nitride, tantalum nitride, ormolybdenum nitride with a thickness from 1 nm to 20 nm.

In FIGS. 5A and 5B, the gate electrode layer 510 may be formed over thegate dielectric layer 170. The gate electrode layer 510 may comprise aconductive material and may be selected from a group comprising ofpolycrystalline-silicon (poly-Si), poly-crystalline silicon-germanium(poly-SiGe), metallic nitrides, metallic silicides, metallic oxides, andmetals. Examples of metallic nitrides include tungsten nitride,molybdenum nitride, titanium nitride, and tantalum nitride, or theircombinations. Examples of metallic silicide include tungsten silicide,titanium silicide, cobalt silicide, nickel silicide, platinum silicide,erbium silicide, or their combinations. Examples of metallic oxidesinclude ruthenium oxide, indium tin oxide, or their combinations.Examples of metal include tungsten, titanium, aluminum, copper,molybdenum, nickel, platinum, etc.

The gate electrode layer 510 may be deposited by CVD, sputterdeposition, or other techniques known and used in the art for depositingconductive materials. The thickness of the gate electrode layer 510 maybe in the range of about 200 angstroms to about 4,000 angstroms. The topsurface of the gate electrode layer 510 usually has a non-planar topsurface, and may be planarized prior to patterning of the gate electrodelayer 510 or gate etch. Ions may or may not be introduced into the gateelectrode layer 510 at this point. Ions may be introduced, for example,by ion implantation techniques.

FIG. 6 illustrates the patterning of the gate electrode layer 510 andthe gate dielectric layer 170 to form the gate 180 and dummy gates 182.The gates may be formed by depositing and patterning a gate mask (notshown) on the gate electrode layer 510 using, for example, depositionand photolithography techniques known in the art. The gate mask mayincorporate commonly used masking materials, such as (but not limitedto) photoresist material, silicon oxide, silicon oxynitride, and/orsilicon nitride. The gate electrode layer 510 and the gate dielectriclayer 170 may be etched using plasma etching to form the patterned gatesas illustrated in FIG. 6. In another embodiment, the outside dummy gates182 are not formed, but just the dummy gates 182 that are between thesource/drain regions 140 and the body contacts 150.

In FIG. 7, the formation of source/drain regions 140 and the bodycontacts 150 is illustrated. The source/drain regions 140 and the bodycontacts 150 may be doped by performing implanting process 710 toimplant appropriate dopants to complement the dopants in the fin 120. Inan embodiment, the fin 120 is implanted (as discussed above withreference to FIGS. 2A and 2B) with p-type dopants such as boron,gallium, indium, or the like, the source/drain regions are implantedwith n-type dopants such as phosphorous, arsenic, antimony, or the likeand the body contacts 150 are implanted with p-type dopants. Thesource/drain regions 140 are implanted using the gate 180 as a mask andthe body contacts 150 are implanted using the dummy gates 182 as a mask.In some embodiments, the doped source/drain regions 140 and the dopedbody contacts 150 may be annealed to promote diffusion of the dopantimpurities into the fin 120. In an embodiment, as shown in FIG. 7, thesource/drain region 140 and the nearest body contact 150 may have adistance 720 between them of approximately 80 nm and 400 nm.

The body contacts 150 help to provide electrostatic discharge (ESD)protection for the source/drain regions 140. When the body contacts 150are doped p-type and the source/drain regions 140 are doped n-type, ap-n junction is created in the fin 120 area between a source/drainregion 140 and the nearest body contact 150. This p-n junction creates aparasitic body diode from the body contact 150 to the source/drainregion 140 which will allow the body contact 150 to perform ESDprotection with low on resistance. The body contacts 150 may beconnected to an ESD discharging circuit such as a ground or power supplyvoltage. For example, in an illustrative embodiment, the fin 120 isdoped p-type, the source/drain region 140 is doped n-type, the bodycontact 150 is doped p-type, and the distance 720 (see FIG. 7) betweenthe source/drain region 140 and the body contact 150 is about 200 nm. Asone of ordinary skill in the art will appreciation, the distance 720 mayvary depending on the technology node of the device and the requirementsof the circuit.

In another embodiment, the source/drain regions 140 and the bodycontacts 150 may be formed by forming recesses (not shown) in fin 120and epitaxially growing material in the recesses. In an embodiment, therecesses may be formed by an anisotropic etch. Alternatively, therecesses may be formed by an isotropic orientation dependent etchingprocess, wherein tetramethylammonium hydroxide (TMAH) or the like may beused as an etchant. After the recesses are formed, the source/drainregions 140 and the body contacts 150 may be formed by epitaxiallygrowing material in the recesses. During the epitaxy process, etchinggas, such as HCl gas, may be added (as an etching gas) into the processgas, so that the source/drain regions 140 and the body contacts 150 areselectively grown in the recesses, but not on the gates. In alternativeembodiments, no etching gas is added, or the amount of etching gas issmall, so that there is a thin layer of the source/drain regions 140 andthe body contacts 150 formed on the substrate gates. In yet anotherembodiment, the gate 180 and dummy gates 182 could be covered with asacrificial layer (not shown) to prevent epitaxial growth thereon. Thesource/drain regions 140 and the body contacts 150 may be doped eitherthrough an implantation method as discussed above, or else by in-situdoping as the material is grown.

The formation methods of the source/drain regions 140 and the bodycontacts 150 may include atomic layer deposition (ALD), chemical vapordeposition (CVD), such as a reduced pressure CVD (RPCVD), metalorganicchemical vapor deposition (MOCVD), or other applicable methods.Depending on the desirable composition of the source/drain regions 140and the body contacts 150, the precursors for the epitaxial may includeSi-containing gases and Ge-containing gases, such as SiH4 and GeH4,and/or the like, and the partial pressures of the Si-containing gasesand Ge-containing gases are adjusted to modify the atomic ratio ofgermanium to silicon.

In another embodiment, the source/drain regions 140 are formed so as toimpart a strain on the channel region underneath the gate 180. In anembodiment wherein the fin 120 comprises silicon, the source/drainregions 140 may then be formed through a SEG process with a material,such as silicon germanium, silicon carbon, or the like that has adifferent lattice constant than the silicon. The lattice mismatchbetween the stressor material source/drain regions 140 and the channelregion formed underneath the gate 180 will impart a stress into thechannel region that will increase the carrier mobility and the overallperformance of the device. The source/drain regions 140 may be dopedeither through an implantation method as discussed above, or else byin-situ doping as the material is grown.

FIG. 8 illustrates the formation of gate spacers 190 on opposite sidesof the gates and the formation of the electrode layer 160. The gatespacers 190 are typically formed by blanket depositing a spacer layer(not shown) on the previously formed structure. The spacer layer maycomprise of SiN, oxynitride, SiC, SiON, oxide, and the like and may beformed by methods utilized to form such a layer, such as chemical vapordeposition (CVD), plasma enhanced CVD, sputter, and other methods knownin the art. The gate spacers 190 are then patterned, preferably byanisotropically etching to remove the spacer layer from the horizontalsurfaces of the structure.

The electrode layer 160 may comprise a conductive material and may beselected from a group comprising of polycrystalline-silicon (poly-Si),poly-crystalline silicon-germanium (poly-SiGe), metallic nitrides,metallic silicides, metallic oxides, and metals. The electrode layer 160may be deposited by CVD, sputter deposition, or other techniques knownand used in the art for depositing conductive materials.

In another embodiment, the source/drain regions 140 may comprise alightly doped region and a heavily doped region. In this embodiment,before the gate spacers 190 are formed, the source/drain regions 140 maybe lightly doped. After the gate spacers 190 are formed, thesource/drain regions 140 may then be heavily doped. This forms lightlydoped regions and heavily doped regions. The lightly doped regions areprimarily underneath the gate spacers 190 while the heavily dopedregions are outside of the gate spacers 190 along the fin 120.

FIG. 9 illustrates a cross-sectional view of a second embodiment inwhich the finFET device comprises a double-gate configuration with threesource/drain regions 140. In this embodiment, one source/drain region140 laterally separates the two gates 180 and the two other source/drainregions are on the outer sides of the two gates 180. Similar to theembodiment in FIG. 7, the outer source/drain regions 140 are laterallyseparated by a distance 720 from the nearest body contact 150.

The embodiment in FIG. 9 may begin formation as shown in FIGS. 2Athrough 5B. After the gate electrode layer 510 is deposited (see FIGS.5A and 5B), the gate electrode layer 510 is patterned to form the twogates 180 and the four dummy gates 182 (see FIG. 9). After the gates 180and the dummy gates 182 are formed, the source/drain regions 140, thebody contacts 150, the gate spacers 190, and the electrode layer 160 maybe formed. The formation of the source/drain regions 140, the bodycontacts 150, the gate spacers 190, and the electrode layer 160 has beendescribed above with respect to FIGS. 7 and 8, and hence is not repeatedherein.

FIG. 10A illustrates a top-down view of an embodiment of the finFETdevice, wherein the device has substrate body contacts 910 above andbelow the fin structure. As shown in FIG. 10A, the substrate bodycontacts 910 are separated from the fins 120 and gates 180 and 182 bythe isolation region 130. These substrate body contacts 910 help toprovide ESD protection to the finFET device. FIG. 10A shows five fins120 spaced apart from each other that are substantially parallel to eachother. Each fin 120 has source/drain regions 140 and body contacts 150.Additionally, the source/drain regions 140 and the body contacts 150 ofeach fin 120 are on opposite sides of the dummy gate 182. The gate 180and the dummy gates 182 are substantially parallel to each other and areperpendicular to the fins 120. FIG. 10B is a cross-sectional view alongthe line YY from FIG. 10A. FIG. 10B shows that the substrate bodycontacts 910 are separated from the fins 120 and the dummy gate 182 bythe isolation region 130.

Although the present embodiments and their advantages have beendescribed in detail, it should be understood that various changes,substitutions, and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims. Moreover, the scope of the present application is not intendedto be limited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods, and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. A method of forming a semiconductor structure,the method comprising: forming a semiconductor fin on a substrate;forming a first gate structure on a top surface and sidewalls of thesemiconductor fin; forming a second gate structure on the top surfaceand sidewalls of the semiconductor fin, the second gate structure beinglaterally spaced from the first gate structure; forming a third gatestructure on the top surface and sidewalls of the semiconductor fin, thethird gate structure being laterally spaced form the first gatestructure in a direction opposite from the second gate structure;forming a first source/drain region in the semiconductor fin, the firstsource/drain region being laterally between the first gate structure andthe second gate structure; forming a second source/drain region in thesemiconductor fin, the second source/drain region being laterallybetween the first gate structure and the third gate structure; andforming a first body contact in the semiconductor fin, the first bodycontact being laterally spaced from first source/drain region, thesecond gate structure being laterally between the first source/drainregion and the first body contact.
 2. The method of claim 1, wherein theforming the first source/drain region comprises: patterning thesemiconductor fin to form a first recess; and epitaxially growing thefirst source/drain region in the first recess.
 3. The method of claim 1further comprising: forming a second body contact in the semiconductorfin, the second body contact being laterally spaced from secondsource/drain region, the third gate structure being laterally betweenthe second source/drain region and the second body contact.
 4. Themethod of claim 1 further comprising: forming a third source/drainregion in the semiconductor fin, the third source/drain region beinglaterally spaced from the second source/drain region in a directionopposite the first source/drain region.
 5. The method of claim 1,wherein the second gate structure partially overlaps the first bodycontact.
 6. The method of claim 1 further comprising: forming anisolation region in the semiconductor fin adjoining the first bodycontact, the second gate structure partially overlapping the isolationregion and partially overlapping the first body contact.
 7. The methodof claim 1, wherein the first gate structure is an active gate, and thesecond gate structure and the third gate structure are dummy gates. 8.The method of claim 1 further comprising: implanting the semiconductorfin with dopants of a first conductivity type; implanting the firstsource/drain region with dopants of a second conductivity type; andimplanting the first body contact with dopants of the first conductivitytype.
 9. The method of claim 1, wherein a first portion of thesemiconductor fin extends from the first body contact to the firstsource/drain region, the first portion being a semiconductor material.10. A method comprising: forming a fin extending from a substrate;forming a first gate and a second gate over the fin; forming a firstsource/drain region in the fin between the first and second gates; andforming a first body contact in the fin, the second gate partiallyoverlapping the first body contact.
 11. The method of claim 10 furthercomprising: forming a third gate over the fin between the firstsource/drain region and the first body contact.
 12. The method of claim11, wherein the third gate is directly over a first portion of the fin,the first portion being a semiconductor material.
 13. The method ofclaim 10 further comprising: doping the fin with dopants of a firstconductivity type; wherein the forming the first source/drain region inthe fin comprises doping the first source/drain region with dopants of asecond conductivity type; and wherein the forming the first body contactin the fin comprises doping the first body contact with dopants of thefirst conductivity type.
 14. The method of claim 13, wherein the firstconductivity type is p-type and the second conductivity type is n-type.15. The method claim 10 further comprising: forming a first isolationregion in the fin, the second gate partially overlapping the firstisolation region.
 16. The method of claim 10 further comprising: forminga fourth gate over the fin; forming a second source/drain regionlaterally between the first gate and the fourth gate; and forming asecond body contact in the fin, the fourth gate partially overlappingthe second body contact.
 17. The method of claim 16, wherein the firstgate is an active gate, and wherein the second and fourth gates aredummy gates.
 18. A method comprising: forming a semiconductor fin raisedabove a substrate; forming a first active gate over the semiconductorfin; forming a first dummy gate over the semiconductor fin; forming afirst source/drain region in the semiconductor fin between the firstactive gate and the first dummy gate, the first source/drain regionbeing adjacent a first side of the first dummy gate; and forming a firstbody contact in the semiconductor fin adjacent a second side of thefirst dummy gate, the second side being opposite the first side.
 19. Themethod of claim 18, wherein the first dummy gate is over a first portionof the semiconductor fin, the first portion extending from the firstbody contact to the first source/drain region, the first portion being asemiconductor material.
 20. The method of claim 18 further comprising:forming a second dummy gate over the fin; forming a second source/drainregion in the semiconductor fin between the first active gate the seconddummy gate; and forming a second body contact in the semiconductor finadjacent the second dummy gate.